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Special Test

Derbolowsky Test

Derbolowsky test is used to assess a leg length difference: an advancement phenomenon with the patient supine.

How Derbolowsky Test is Performed?

  • The patient is supine.
  • The examiner grasps both ankles, palpates the patient’s medial malleoli with each thumb, and evaluates the relative level and rotation of the medial malleoli using the positions of the thumbs as reference.
  • The patient is asked to sit up; either the examiner may help the patient do so, or the patient may use his or her hands for support.
  • The legs should be lifted off the table to prevent interference.
  • Then the level and rotation position of the malleoli are again evaluated.
  • Lastly, the patient is asked to bend the trunk maximally forward to come as close to the extended knees as possible.
  • The derbolowsky test should be carried out several times to prevent false-positive test results due to muscle tension.

What does a positive Derbolowsky Test mean?

  • Forward advancement in the supine position suggests pelvic rotation.
  • Where there is a motion restriction in the sacroiliac joint without any play between the sacrum and ilium, the ipsilateral leg will be longer when the patient sits up and apparently shorter or the same length as the other leg when the patient is supine.
  • The examiner measures the difference in the level of the two malleoli, which previously were at the same level.

The differential diagnosis should consider whether something other than a motion restriction in the sacroiliac joint may be causing the variable leg length difference.

Possible such causes include shortening of the hamstring muscles or genuine anatomical leg lengthening or shortening.

Pain during the Derbolowsky Test could suggest loosening of the sacral structure, muscular foreshortening, or neurologic pain from a protruding or herniated disk.

Notes

  • Derbolowsky test is considered to be diagnostically significant if the difference in levels amounts to at least 1 to 2 cm.
  • When one sees larger differences in connection with myalgic pain, then one should consider shortened hamstring muscles as a cause.
  • If the difference is greater than 5 cm combined with symptoms of radicular pain and pelvic rotation with compensatory flexion of the knee, then one should consider vertebral disk dysfunction.

Leg Length Discrepancy

When examining leg length, one must consider the possibility of apparent lengthening or shortening due to an abduction or adduction contracture.

  • In the presence of an abduction contracture of the leg at the hip, the patient can only bring his or her legs into parallel alignment by tilting the pelvis. This pushes the normal hip upward, making that leg appear shortened.
  • The adduction contracture has an analogous effect, although in this case the affected leg appears shortened.
See Also: Leg Length Measurement

Assessing Leg length Difference LLD

1. Tape measure:

It measures the length of the lower extremity by measuring the distance between the anterior superior iliac spine (ASIS) and the medial malleolus, it’s also called “direct method” for measuring LLD (True Leg Length).

An apparent leg length can be measured from the umbilicus to the medial malleoli of the ankle.

In some cases, lengths of the appendicular skeleton may be equal, but apparent shortening may result from pelvic obliquity or contractures around the hip and knee joints.

2. Standing on Blocks:

This method levels the pelvis of the standing patient by placing blocks of known height under the short limb. It’s also called the “indirect method” for measuring LLD.

3. Imaging Methods:

  • Plain Radiography: with a full-length standing AP radiograph of the lower extremity, the x-ray beam centered at the knee joint from a distance of approximately 180 cm, while the patient stands with both patellae pointing anteriorly.
  • Computed Radiography
  • MRI Scan

Reference

  • Clinical Tests for the Musculoskeletal 3rd Ed. Book
  • Division of Pediatric Orthopaedics, Department of Orthopaedics, UMDNJ—New Jersey Medical School, Newark, NJ USA 1

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